1. Field of the Invention
This invention relates to an assembly that includes a container, a seal extending over an outlet of the container and a cap detachably connected to the container over the seal.
2. Description of the Related Art
Multiple-barrel dispensing containers such as double barrel syringes are useful for storing different reactive components that, once dispensed, are mixed together to form a desired composition. As an example, a double barrel syringe for dispensing dental impressioning material may hold a catalyst component in one chamber and a base component in another chamber. Portions of each impressioning component are simultaneously dispensed for immediate mixing and measuring of the separate components is unnecessary.
One example of a double barrel dispensing syringe is described in U.S. Pat. No. 4,538,920 which is assigned to the assignee of the present invention. The syringe has two interconnected plungers for simultaneously dispensing proportioned amounts of material from each barrel. An exit conduit is releasably connected to the syringe and has a plurality of helical mixing elements so that the components are thoroughly mixed once discharged from the exit conduit and mixing by hand may be avoided.
Typically, only a portion of the components are dispensed at any one time from the barrels of the syringe shown in U.S. Pat. No. 4,538,920, and it is often desirable to keep the side-by-side outlets of the syringe covered between dispensing operations in order to prevent undue hardening or drying of the component materials in the barrels. In the past, certain dispensing syringes have been provided with a cap having flanges that releasably lock into recesses next to the two outlets of the syringe as the cap is turned approximately ninety degrees relative to the syringe. The cap carries an internal seal that covers both of the outlets when coupled to the syringe.
However, many conventional caps for double barrel syringes may contribute to cross-contamination of the remaining materials within the barrels both before and after initial use of the syringe. For example, if a small quantity of material of one barrel is deposited on the seal within the rotatable cap mentioned above, the material may contact and react with material in the other barrel as the cap is re-coupled onto the container after initial use. As another example, the recesses holding the flanges of the rotatable cap may elongate, enabling the migration of material across the seal from one outlet to the other. Although in either example the amount of reacted material and resulting cross-contamination may be relatively small compared to remaining material within the barrels, such cross-contamination may result in a certain amount of polymerization that might hinder passage of the material along the tortuous path presented by the helical mixing elements.
Users of double barrel syringes are often provided with instructions that indicate that good results are attained when the exit conduit with the helical mixing elements is left connected to the container after use and the cap is not re-used. In this manner, mixed material within the exit conduit hardens and provides a seal that is generally more satisfactory than a seal that would be established by re-use of the cap. Immediately prior to the next use, the exit conduit is disposed of and a new exit conduit is connected to the container in its place. Unfortunately, some individuals do not follow the written instructions and attempt to re-use the rotatable cap, possibly leading to the problems mentioned above.
A push-on cap having a protruding orienting section for use with a double barrel dispensing container having a threaded outlet is described in U.S. Pat. No. 4,974,756, assigned to the assignee of the present invention. The orienting section ensures that the cap is in a certain orientation relative to the container each time that the cap is coupled to the container, so that the likelihood of cross-contamination is reduced. However, while the cap described in U.S. Pat. No. 4,974,756 is highly satisfactory for use with many types of materials, there are certain instances where it is desired to discourage re-use of a cap and instead encourage the user to leave the exit conduit in place after a dispensing operation.